Remote control system



Nov. 7, 1944. F. H. SHEPARD, JR 2,362,412

' REMOTE CONTROL SYSTEM Filed June 25, 1938 '7 Sheets-Sheet l INVENTOR l F. H. SHE ARD JR.

ATTO RN EY 7, 1944- F. H. SHEPARD, JR 2,362,412

REMOTE CONTROL SYSTEM Filed June-25, 1938 7 Sheets-Sheet 2 INVENTOR F- H. SHEP D JR.

H4 Mk ATTO RN EY Nov. 7, 1944.

F. H. SHEPARD, JR 2,362,412

REMOTE CONTROL SYSTEM FiledJune 25, 1938 7 Sheets-Sheet 3 k A 93 as sag/94 s9 95 \,L4

. r 4 22 102/ $03 I q B M 81 -79 l'hy d VA 1? 102 a! L LC 7 INVENTOR F. H. SHEPARD JR. 7k W/L/ TORNEYS Nov. 7, 1944. F. H. SHEPARD, JR 2,362,412

REMOTE CONTROL SYSTEM Filed June 25, 1938 '1 She ets-Sheet 4 EP RDJR.

INVENTOR F. H. SH BY 7% ATTORNEY SQ A 3w 4 2: Q? M. g

Nov. 7, 1944.

F H. SHEPARD, JR

REMOTE CONTROL SYSTEM 7 Sheets-Shet .5

Filed June 25, 1938 INVENTOR F. H. SHEPARD JR;

AT TORNEYS Nov. 7, 1944. F. H. SHEPARD, JR

REMOTE CONTROL SYSTEM Filed June 25, 15338 7 Sheets-Sheet 6 INVENTOR F. H. SHEPA 0 JR.

ATTORNEY Nov. 7, 19 44.

"F H. SHEPARD, JR

REMOTE CONTROL SYSTEM Filed June 25, 1938 '7 Sheets-Sheet ,7

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ATTORNEY Patented Nov. 7, 1944 REMOTE CONTROL SYSTEM Francis 11. Shepard, Jr., Rutherford, N. 1., assignor to Radio Corporation of America, a corporation of Delaware Application June 25, 1938, Serial No. 215,731

8 Claims.

The present invention relates broadly to remote control apparatus and more particularly to a system for controlling the operation of a stepswitch from a remote point.

In a more specific sense the invention relates to a system for the complete remote control operation of radio receivers over a power supply line without making use of any auxiliary wires between the radio receiver and the remote control point.

An object of the invention is to provide a novel system of remote control operation of a stepswitch by transmitting control electrical impulses to cause the operation of the step-switch to any one of its various contact positions or steps and thereby provide for the selective operation of any number of devices associated with the various contacts of the step-switch. When the invention is applied to a radio receiver the stepswitch may be utilized to turn the receiver on" and off, to control the volume, and to tune to various stations. In conjunction with a radio receiver of the push-button" type, the stepswitch may be utilized to perform the equivalent functions performed by pressing the various push-buttons of the receiver.

It is generally known that radio receiving apparatus may be controlled: by the operation of electrical devices the operations of which are initiated by the closing of contacts operated by push buttons. In such systems the various push buttons are used to initiate or to cause the radio set to perform certain predetermined functions. In order to provide practical remote control for radio receivers and the like it has heretofore been necessary to use a cable containing a multiplicity of wires for connecting the control mechanism at the remote point to the control mechanism at the radio set. In general, it has been found that a cable is both inconvenient and undesirable. This invention provides an arrangement which eliminates the necessity for a cable by providing a carrier operated relay device which may be used to operate contacts or to supply power to operate a step-switch mechanism connected so as to perform the same functions as are now performed by pressing the various buttons of a push-button receiver, i. e.. shorting the button operated switches to get the same effect as is obtained by operating a button of one of the known conventional pushbutton systems. As the relay is caused to operate by the reception of a carrier, this carrier can consist of pulses of radio frequency received by direct radiation through space or be guided over the existing power lines. The relay may eonsist of a thermionic device which will control enough energy directly to operate a step-switch or it may operate an electrical mechanical relay which will in turn control interrupt energy to the step switch.

In using a step switch to control a conventional push button tuned radio set, there or three factors that must be taken into account. First, the step switch must be pulsed one step at a time until the proper connections are made, i. e., until the switch corresponding to the proper push button is shorted; secondly, the step switch must remain in this position at least until the mechanism at the radio receiver has had time to complete the operation called for; and. thirdly, the return mechanism to bring the step switch back to its home position must be made to operate after all these functions have been performed.

The invention provides means to render the return mechanism on the step switch inoperative during the pulsing or stepping up of the step switch and also until the operation called for has been completed. After this is completed, the return mechanism returns the step switch to its home or initial starting position. In this way there will be a standard point or home position on the step switch from which each called for operation will start.

The invention will be more readily understood by referring to the following detailed description and the accompanying drawings. In the drawings,

Fig. 1 is a circuit diagram of a carrier operated relay utilizing a cold cathode are or glow discharge tube;

Fig. 2 illustrates an arrangement such as is shown in Figure 1 used to operate a step-switch which in turn controls the operation of a pushbutton type radio receiver;

Figs. 3a and 3b are circuit diagrams of two preferred arrangements of remote control units used to generate the proper number of impulses of control carrier and impress them upon a network;

Fig. 30 illustrates a form 01 a remote control unit shown in Fig. 3b but adapted to transmit radio control waves through space by means of an antenna; I

Fig. 3d illustrates a remote control unit especially adapted for short range work;

Fig. 4a illustrates a vacuum tube carrier operated relay acting on a step switch to control the operation of a push button type radio receiver;

Fig. it) illustrates a system like that shown in Fig. 4a except that it includes an antenna arranged to intercept the control energy;

Fig. 5 illustrates a circuit utilizing a two element glow or are discharge tube; and,

Fig. 6 illustrates the use of a three element gas tube for operating a step-switch.

In the carrier operated relay illustrated in Figure 1, a cold cathode arc discharge tube I is used which is available commercially and which has power handling capabilities sumcient to operate directly an insensitive relay such as a step switch requiring large amounts of energy in its stepping coil. The tube 1 is provided with four elements comprising a cold electrode II, a first grid II, a second grid i1 and an anode or plate I8. The cold electrode HS in this type tube, sometimes referred to as a -cold cathode," will emit electrons in a manner well knownto those familiar with such tube types and the art to which they pertain. In one particular tube of this type the cold cathode is activated with caesium and the tube is filled with an inert gas such as argon or neon or both. The tube has the property of conducting very large currents with an extremely small tube drop as well as the property that a relatively high voltage may be applied between the anode and the cathode without any conduction occurring until a discharge is initiated between any other two elements within the tube.

In Fig. 1, conductors I and 2 are intended to ,represent an A. C. light and power supply line such as is usually found in buildings supplied from a commercial electric light and power system. The space path of tube 1 is eflectively connected across the power line conductors i and 2 by the connection of anode l8 of the tube to conductor 3 through a relay winding l I and the connection of electrode i5 directly to conductor 4. A by-pass condenser i is shunted across the relay winding l i. Grid ll of tube 1 is connected to both power line conductors in one case through an inductor l and conductor 4 and in the other case through the condenser 9 and conductor 3. Condenser 9 and inductor Ill form a series resonant circuit across the power supply line which acts to build up control carrier currents lm pressed upon the power Supp y line as will be described hereinafter. Grid ll of the tube 1 is, in effect, connected to both power line conductors i and 2 by connection thereof to a tap 6 on an impedance 5 connected between conductors 3 and 4. Relay winding ll operates a switch II which may be used to control any electrical circuit connected to it through terminals II and H.

From a study of the circuit shown in Fig. 1, it is clear that the power line voltage is impressed between the anode I 8 and cathode Ii of tube 1 and that the position of tap 6 on resistor 5 determines the voltage impressed upon the grid H. A discharge initiated between grid l8 and grid i? creates ions within the gas which thereupon enable a discharge to be initiated or take place between the cathode ll and plate ll. Once a discharge is initiated it can be extinguished only by removal of the voltages to the elements. As the. circuit is operated on the raw alternating current available across the power line I, 2, the discharge in tube I is extinguished every time ll becomes negative with respect to IE, and, therefore, must be re-initiated once each cycle of the supply. The design of the tube 1 is such that discharges taking place in the reverse direction, that is, from i8 to are of limited magnitude due to the shielding action of grids I6 and I1 and poor activation on the anode. Special precautions are often necessary to limit this back current in the manufacture of the tube but since this is not within the scope of the present invention, it will not be further discussed herein. The bias voltage on grid I1 is applied from point 0 on the potential divider I which-may comprise any type of impedance, that is, it may be resistance, capacitance or inductance. In operation the tap i is adJusted along I until the peak value of the potential on grid I1 is slightly less than the value necessary to start a discharge between grid II and grid II or between cathode II and grid H. The structure of the tube is such that extremely high voltages between grid l1 and plate I 8 are necessary to initiate a discharge. The grid I, for frequencies of the power supply, is essentially grounded to the cathode ll through inductance it. However, a carrier voltage of the proper frequency applied across the line I, I will result in relatively high amplitude circulating currents flowing through the series resonant circuit 9, ill in a manner known to those familiar with the art.

Since this high circulating control current will result in a high voltage being built up across inductor In or condenser I, this voltage appears between the cathode II and grid II and is thereby eifectively added to the normal power supply line potential between grid II and grid II with the result that the potential between these grids is increased to such a value that a discharge between grid l6 and grid I! will take place. This discharge is of sufficient magnitude to cause ionization in the tube and thus cause the discharge to take place between the cathode and the anode of the tube which in turn operates the relay H and, hence, switch 12. It is to be understood that this action can only take place during the half cycles of power supply voltage when anode ll is positive with respect to cathode II.

In the form of the invention shown in Fig. 2 for the remote control of a radio receiver, a cold cathode arc discharge tube of the same type as described in Fig. 1 is fired by control carrier pulses on the power supply line and energizes the coil of a step relay and the coil of a quick acting slow release relay. The stepping relay is arranged to perform the various functions performed by pressing the various push buttons of a push button controlled radio receiver after which it returns to its starting position and is ready to receive another train of control pulses. The device shown in Fig. 2 of the drawings is connected to the conductors of the power supply line (not shown) through a polarized plug ii. The tube 1 is associated with the conductors of the power supply line in the same manner as described in Fig. 1. However, in the arrangement shown in Fig. 2 a step coil 22 is connected to the circuit and replaces the relay coil ll of Fig. l and the step coil 22 operates the step switch arm 29 to connect the arm 28 to any one of the contacts 30 through 42 depending upon the number of control carrier frequency pulses received over the power line. The step coil 22 operates a pawl 3M against the pull of a returning spring 300 to turn the ratchet wheel 3" against the force of returning spring "I. Ratchet wheel m is connected to arm 29 through a suitable means represented generally by the dot and dash line 305. In this way the returning spring III also acts. under certain conditions hereinafter referred to, to force the arm 29 back to its home position 30 against stop 30! mounted on disk llll. A quick acting slow release relay winding 2| connected across the step coil 22 acts upon a switch 2| which with a relay-winding 21, a switch 26, a return coil relay winding 24 and a switch 23, forms a series circuit connected between conductors 3 and 4.

The return coil relay 24 when energized operates a dog 392 against the force of a returning spring 303 to release the ratchet wheel 300 and thereby permit spring 31H to return the mechanism including arm 29 to its home position. The operation of switch 23 is controlled by the movable arm 29 which acts to maintain switch 23 open when arm 29 is in the home position 39 and closed at all other positions. For this purpose arm 29 is provided with a depending portion 301 preferably constructed of insulation material which holds switch 23 open when arm 29 is in its home position 39 and allows a spring 308 to close switch 23 in all other positions of arm 29. The operation of switch 25 is controlled by a relay winding 25 connected between the movable arm 29 of the The push button tuning unit has not been shown in detail since such units are well known.

Consequently, only those parts of the unit are illustrated and described which are believed to be necessary for a proper understanding of the present invention. In this device, -as shown schematically by the dash line connection, the shaft of a reversible motor 52 may be coupled either to the shaft of the variable tuning condensers TC of the radio receiver in any suitable manner and to the shaft of the station setting commutators 33-86 inclusive only four of which have been shown for convenience. or to the shaft of the volume control device VC,.depending upon the voltage applied to the motor. The motor may be a 23 volt displaceable armature capacitor type .A. C. motor arranged to be geared to the condenser shaft or to the volume control potentiometer through suitable gear trains. The motor circuits are arranged so as to control the direction in which the motor rotates. The motor is also ar- V ranged so that if an operating voltage of say, 18

shaft. Increasing the voltage to the normal voltage of 23 volts causes the motor to speed up and its armature to be displaced axially in such a direction as to disengage the volume control connection and engage the condenser shaft and the shaft of the station sett ng commutators. A suitable type of motor and connections therefor are described in detail in U. S. Patent to Hopkins 1,999,359 issued April 30, 1937.

The reversible feature of the motor is made use of to operate the volume control shaft in either direction for increasin and decreasing the volume and also to operate the station setting commutators and condenser shaft in either direction so that during a tuning operation the motor seeks a newly called for position via the shortest path. For this purpose, it will be noted that the commutators 34 through 69 are split, that is, each one is made in two sections separated by a strip of insulating material. The respective halves of each commutator are connected to the conductors 3| and 92 which in turn are connected respectively to the motor windings 53 and 54 of the motor assembly. Wipers 43 through 46 cooperate with the station setting commutators and determine the direction in which the motor shaft is turned and also stop the motor when on the insulation strips between the segments. The motor energizing circuit derives its energy from transformer 55 which is connected to the power supply line in any suitable manner. A suitable type of motor and commutator assembly is fully described in U. S. Patent to Garrett 1,956,419, issued April 24, 1934. A further description of the type of motor and control circuits adapted to be operated in the device shown in Fig. 2 will be found in the U. S. Patent to Seeley 2,245,829, issued June 17, 1941.

The "on and off switch for the radio receiver is shown generally at 51. This switch is controlled by the two windings 56 and 58 and staysput in either position after operation. It will be noted that the winding 56 is connected between terminal 39 of the step switch and arm 29 through a conductor 60, the secondary of the transformer 55, switch 28 and winding 25. The winding 58 on the other hand is connected between terminal 41 of the step switch and arm 29 through conductor 59, the secondary of the power transformer 55. switch 23 and winding 25. Considering now the terminals 39 through 42 of the station switch, it will be noted that terminal 39 is not *connected to anything, that is, it is left blank; terminal 3| is connected to arm 29 through the voltage reducing resistor 41, motor winding '53, thesecondary of transformer 55, switch 28 and winding 25; terminal 32 is left blank; terminal .33 is connected to arm 29 through voltage reducing resistor 43, motor winding 54, secondary of transformer 55, switch 23 and winding 25; terminal 34 is left blank; terminal 35 is corniected to the wiper or brush 43 which cooperates with the station setting commutator 66. Terminal 35 may be connected to arm 29 through either one of two paths depending upon the position of the station setting commutator 96. For instance, the terminal 35 may be connected to arm 29 through the brush 43, the left hand section of the station setting commutator 66, the conductor connecting this section of the station setting commutator to bus bar 5!, conductor 50, motor winding 53, secondary of transformer 55, switch 28 and winding 25. If the station setting commutator is rotated, let us say, degrees from the position shown, then terminal 35 would be connected to arm29 through a circuit comprising the brush 43, the other half of the station setting commutator 66, the connection between said other half and bus bar 62, conductor 49, motor winding 54, secondary of power transformer 55, switch 23 and winding 25.

The above shows clearly how the reversing action of the motor takes place depending upon which half segment of the station setting commutator is in contact with the brush 43 at the time the arm 29 contacts the corresponding contact point 35. It should be noted that these station setting commutators are set so that the condenser is rotated to the proper setting for the particular station set for, when the insulation portion of the commutator corresponding to the desired station reaches the brush at which time the motor circuit is, of course, interrupted. The connections of terminals 36, 31 and 33 to arm or sliding contact 29 through either of two paths is similar to that described above in conjunction with the terminal 35. It is only necessary to note that each one of the station setting commutators is set so as to break the motor circuit at a different position corresponding to some different station desired. Terminal 39 is connected to arm 29 through the conductor 60, relay winding 56,

secondary of power transformer 55, switch 28 and relay winding 25. Terminal 40 is left blank, terminal 45 is connected to arm 29 through the conductor 59, winding 58, secondary of power transformer 55, switch 28 and relay winding 25. Terminal 42 is left blank.

Referring to Fig. 2 the operation of the system is as follows:

To energize or turn on the receiver the user will dial No. 9- on his control switch at the remote point which will send out a train or nine pulses of control carrier frequency on the power line across which there is connected the series tuned circuit including inductance II and condenser 9. As this circuit is resonant to the freuucncy of the control carrier, a carrier frequency voltage will be built up across inductor l and condenser 9 and will appear between the grid I8 and the cold cathode of the tube I. It will also appear between grid l6 and grid I]. By adlusting contact 6 or potentiometer resistance 5 a potential is established between grids l2 and II that just fails to strike an arc therebetween on the positive half cycles when no signal carrier voltage is on the line, When the carrier frequency voltage appears due to the tuned circuit an increased voltage is produced between grids i6 and H, the breakdown potential between these elements is exceeded and a glow occurs. This creates ionization within the tube 1 which causes a glow to be established between cathode l5 and plate Hi. The glow discharge changes into an arc discharge as the current rises and the plate to cathode drop in the tube drops to the arc dis charge potential. This discharge of tube I extinguishes itself when the plate voltage drops below zero, that is, when the potential of plate I! becomes negative with respect to the cathode due to the alternating current supply. The discharge will be reestablished on the next positive half cycle of the power supply line voltage, the control carrier frequency being still present on the line. Part of the current passed by the tube I passes through the coil or the step relay 22 and part passes through the coil of the quick acting slow release relay 20. The step relay 22 advances the step switch arm 29 one step or notch for every of carrier energy received, while the operation of the quick acting slow release relay 20 causes the normally closed switch 2! to open. As soon as the step switch arm 29 is advanced away from its home position 30, normally open switch 23 is automatically closed. However, the return coil 24 cannot become energized because switch H of slow release relay 2a is open as long as the dialing pulses continue to be received by the tube 1. In the assumed case the nine pulses advanced the arm 29 step by step to the contact 38 which energized relay 5G and closed the switch 51 which is the on-of! switch of the receiver. This energized relay 25 and opened'switch 26, thus preventing operation of the return or homing relay 24. The user next would transmit one more pulse which would step the arm 29 up to the blank contact 40. Thisinterrupts the current in coil 25 and energizes relay 24 and the arm homes to contact 20. The relay 24 is then deenergized by opening switch 23. In thereafter selecting a desired station the step switch is advanced, say, five notches to point 25 by dialing five pulses, the tuning mechanism of the push button controlled radio begins to operate and the motor 52 draws the ful current which unclutches the motor from the volume control and clutches it to the tuning control. The motor current passes through relay '25 and causes normally closed switch 26 to open. Contact 26 is in series with the return coil 24 on the step switch and so provides additional means to prevent the return coil from operating its switch 23. As the dial pulses have ceased before the motor 62 has completed the tuning operation, relay 20 after a short period of time drops out and causes contact 2| to close. The return coil 24, however, cannot operate because contact 28 is open as Just described. When the motor 52 moves the tuning device and the commutator 62-66 to the point where the brush 43 on commutator. will rest on the insulated segment of the commutator 6O the'current to the tuning motor 52 will be interrupted, hence, stopping the flow or current through relay 25 which in turn causes closure of switch 26 thereby causing energization of the return coil 24. Energization of return coil 24 causes the step switch arm to drop back to its home position thereby opening switch 22. When switch 22 is opened the return coil is deenergized and the step switch is ready for another operating cycle.

During the time that the return coil is energized and the step switch arm is returning to its home position 30, the relay coil 21 is energized causing its switch 22 to open. This prevents the tuning mechanism on the push button controlled radio from drawing any current during the time that the slider 29 on the step switch comes in contact with the other contact points on its way back to the home position and thus prevents the radio from being detuned during the return part of the cycle.

To obtain the desired volume the user will dial, say, one pulse and this will step the arm 29 to point II and since the motor 52 is energized through resistor 41' ii. rotates in one direction with reduced voltage applied to it. As previously pointed out, the construction of the motor 52 is such that with roll voltage applied, the armature is displaced against a spring causing it to engage with the receiving set tuning mechanism. If the voltage applied to the motor is insuflicient to cause the armature to displace the spring the tuning mechanism is unclutched from and the volume control is clutched to the motor and is operated. Current drawn irom the motor during this operation passes through the relay 2! and prevents the return mechanism from working as explained above.

When the desired volume change has taken place another pulse is dialed at the control point which causes the step switch to advance another notch to position 22 which is blank. This allows relay 2! to release closing switch 22, causing the return coil 24 to be energized and the step switch to return to the home position. Where it is desired to change the volume in the other direction three pulses are dialed at the controlling pointwith the result that the step switch advances to the third position 22. Since in this case the winding 54 of the motor is energized through the resistor 48, the volume control is operated in the opposite direction. When the volume has been changed the desired amount, another pulse is dialed, the step switch advances to the position 24 which is blank, which cuts 01! the current through relay 25, allows switch 26 to close and the return coil 24 or the step switch to be energized and cause arm 29 to be returned to the home position 30.

It is to be understood that operating the relays with alternating current may cause undesirable chattering so that under these circumstances it is desirable to shade relays 28, 22, 24, 25 and 21 in any suitable manner; An efiective shading action may be obtained by winding one or more turns of uninsulated copper wire around a part 01 the magnetic coil or each relay.

Figure 3a illustrates a circuit arrangement used to generate the control carrier frequencies and to apply the proper number of pulses thereof to the power line in accordance with the control action desired. In this circuit a quick heating cathode type tube 88 is connected in an oscillator circuit in such a manner that the circulating tank currents pass through the power line. This method of use or the oscillator automatically matches, to a limited degree, the output of the relatively high impedance oscillator tube to the relatively low impedance the power line, thus, coupling a sufficient amount or the generated high frequency energy into the power line to provide the desired controlling action. The filament 18 of the oscillator tube 88 is heated by A. C. power line current passing through a suitable resistance which may be a lamp 18 in series with the filament 18. Plate voltage is applied through one-half of the tank circuit from one side 84 of the power line. The number of pulses impressed on the power line is controlled by a telephone type dial switch 13. An RCA type 99 tube is admirably adapted for use in this circuit since this tube has a thoriated tungsten filament which is very quick in coming up to operating temperature. Because of this, it is possible to use the contact 1| of an automatic telephone type dial switch 18 to light the filament, it being understood that switch 1i is closed the moment the dialing mechanism is moved away from the home position. Contact 12o! the telephone dial mechanism 13 is used to interrupt the plate circuit or tube 85 in accordance with the number of pulses it is desired to transmit. It is to be understood that it a slow heater type filament tube is used in this circuit a manually operated switch must be used (see switch 91 of Fig. 3b) to replace or supplement the contact 1| of the telephone dial switch 13 so that the filament of the tube can be brought up to its required'temperature before starting operation oi! the dialing mechanism. Contact switch 12 is closed during the return of the dial to its home position, the number of pulses being in accordance with the number dialed. Since the dialing mechanism is common practice in tele phone work it is thought that it need not be described in detail herein.

For certain purposes to be hereinaitermentioned, it is convenient to provide the remote control unit with a switch other than the telephone dialing device which will automatically transmit one or two impulses over the power line. For this purpose the oscillator circuit of Fig. 3a is provided with an auxiliary switch device comprising a switch including an operating handle 88 and a pair 01' movable elements 88 and 81 connected for simultaneous operation by means schematically shown by the dash line connection. The element 88 cooperates with three switches 88, 84 and 88 and the arms 81 cooperates with two sets of contact strips 88a, 98b, and 9m, slb. The arm 81 is preferably constructed so that its lower portion is composed of conducting material so that in any position other than the released position which is that shownin the drawings, the cooperating bars are short-circuited. The movable elements of the three switches 93, 94 and 88 are each connected to conductor 18. The tlxed contacts of the three switches are connected to the line 84. Contact strips a and 91a are connected to the conductor 10 through conductor 82 and contact strips Bib and 88b are connected to the conductor 15. In order to limit the movement of the element 86 the fixed contacts 88 and 88 of switches 88 and 85 respectively are made so as to act as stops for this purpose. The movement of the arm 81 is limited by the stops 88 and 81 which are preferably constructed of insulation material so as to avoid short-circuiting the contact bars. Movable elements 88 and 81 of the switch are normally maintained in the released position shown, by any suitable resilient means not shown. It will be seen that when the handle 88 is rotated clockwise the oscillator will transmit a train of oscillations as long as the switch handle is held so that the switch 88 is closed and the contact bars 91a and llb are short-circuited. Short-circuiting of the contact bars is the same as closing switch 1| oi the telephone dial whereas closure of switch 98 is the same as closing switch 12 of the telephone dial. From the above it is evident, of course, that the operation of switch handle 98 as described will transmit an impulse over the power supply line and that this pulse will be of controllabie duration, that is, it will last until the switch handle 88 is released. It the switch handle 88 is moved to the limit oi its movement in r the opposite direction to tiiatpreviously described,

then the switch 1| is short circuited when the movable contact 81 short circuits bars 98a, 80b. The plate circuit of the tube will be energized for a short interval of time when the movable contact 88 closes switch 88 momentarily thereby sending out one pulse of carrier energy, then carrier energy is again transmitted over the power line when the movable element 86 closes switch which remains closed as long as 88 is held against stop 88. Carrier energy or an impulse of controllable duration is generated and impressed upon the power line until the switch is allowed to resume its normal position.

In Fig. 3b there is shown an arrangement wherein a switch 91 is provided for the purpose of connecting the tube 88 to the power supply line. Hence, when the switch 91 is. closed the cathode of the tube 88 becomes energized through the circuit comprising conductor 88, switch 81, conductor IIH, tube 14, filament 18 and conductor 88. In this case telephone dial I80 need be provided with only the single switch I02 which is used to make and break the plate circuit of tube 88 to determine the number 0! carrier impulses transmitted over the power line depending upon the number dialed. Since on and off switch 81 is provided, the auxiliary switch need have only one section.

In operation, moving the switch arm 88 clockwise causes the movable element 86 to close switch 88 and to hold it closed as long as 86 is held against stop 88. This causes a train of oscillations to be transmitted over the power supply line. The transmission is stopped as soon as the switch handle 88 is allowed to assume again its normal position as shown. If the switch handle 88 is moved counterclockwise so that arm 88 comes up against the stop 89, a carrier frequency 7 pulse of fixed duration will be transmitted when movable element" closes switch 94. When the movable element 88 passes beyond the switch 84, the switch will open again thereby stopping the pulse of energy transmitted. However, carrier energy will again be transmitted when the element 88 closes switch 85. This last named transmission of carrier energy will be of controllable duration since it will continue as long as the element 86 is held against the stop 89.

The arrangement of the switches 93, 94 and 95 in both Figures 3a and 3b is such that the switches are closed only with movements of element 86 in the directions from the neutral position toward either of the stops 88 and 89 and not in the directions from the stop toward the neutral position.

Fig. 4a illustrates a modification of the invention using a vacuum tube carrier operated relay for operating a step switch to perform certain desired controlling operations. In this modification the three element tube I08 is provided with an anode I I I, a control electrode I I and a cathode I09. The tube isv connected to the power supply line (not shown) by a plug I9. In this case the plug need not be a polarized plug. The plug I9 effectively connects the conductors 3 and 4 to the usual two conductors of a commercial power supply line. Connected across the conductors 3 and 4 is a series resonant circuit comprising inductor I0 and condenser 9. The tube I08 is efiectively connected between the conductors 3 and 4 by a connection from the anode II I to the conductor 3 including a relay winding H3 in series with a carrier frequency choke I01. To energize the cathode I09 one side of it is connected directly to the conductor 4 and the other side is connected to the conductor 3 through a condenser I05 and the choke I01 in series. In this way the cathode I09 of the tube I08 receives its heating current through condenser I 06 and carrier frequency choke I01 from the power line. The control electrode IIO of the tube I08 is connected to a point intermediate condenser 9 and inductor I0 of the series resonant circuit through a resistor I05 shunted by a condenser I04. Resistor I05 is for the purpose of allowing the D. C. potential to leak off condenser I04 within a short period of time but which is relatively long with respect to the power supply cycle. Choke I 01 is utilized to prevent carrier frequency current from passing through and affecting the temperature of the cathode I09. Relay winding II3 acts upon a switch II4 which controls the energization of relay winding Hi. In other words, with the switch II4 closed, relay winding H6 is energized since it is then connected across the conductors 3 and 4. The relay winding IIS acts upon a switch II1 which when closed connects a relay winding II8 across the line 3, 4. The relay winding I I8 also may be connected directly across the line 3, 4 through the intermediary of switch I30. A step switch arm I29 cooperating with a plurality of contacts I20 through I28 is connected to a push button controlled receiver.

This receiver is provided with a reversible motor 52 similar to motor 52 of lFig. 2 having the motor windings 53 and 54, station commutators 63 through 66 cooperating with the contact elements 45, 45, 44 and 48 respectively, "on and off" switch 51 and a motor controlled switch I80. Switch I30 is closed when the armature of motor 52 is displaced sideways during a tuning operation as previously described. The step switch arrangement is somewhat similar to that heretofore described except that four less contact positions are needed than in the arrangement shown in Fig. 2.

The device shown in Fig. 4a operates as follows: Carrier frequency pulses applied across the power supply line to which the plug I9 is connected build up a resonant carrier frequency voltage across inductor l0 and condenser 8 in such a manner that the carrier frequency voltage appears between grid IIO and cathode I09 of tube I08. This carrier frequency voltage appearing between the grid and cathode results in a rectified current being drawn from the cathode I09 to the grid IIO whereby the condenser I04 is charged to a D. C. potential which is comparable in magnitude to the carrier frequency voltage appearing across the inductance l0 in a manner known to those familiar with the art. The negative potential built up across condenser I04 is instrumental in reducing the plate current of tube I08 in such a manner that the pulsing relay coil H3 does not receive sufllcient current to hold the contact I I 4 open.

It should be understood from what has preceded that the carrier generator circuit shown in Figs. 3a and 3b is such that the carrier appears in phase with one half of the power cycle thus making it necessary in some instances, as; for instance, in the arrangement shown in Fig. 2, to polarize the receiving unit with respect to the pulse generating unit. In the circuit shown in Fig. 4a there will be a difference in operation with a change in polarity of the plug I9, that is, when the carrier frequency appears on the half of the power cycle at which the plate voltage to the relay tube is negative, the reduction of plate current on the next half cycle will be greater than would be the reduction in plate current if the. carrier voltage appears during the half cycle that the plate voltage of the relay tube was positive. It is to be noted, however, that this circuit is operable with either polarization. It isto be noted that inductance in the line is included between the cathode and plate of the tube I08. If the plate were by-passed to the side 3 of the line, a simple Hartley oscillator circuit would result and tube I08 would oscillate at a frequency determined by the value of inductance I0 plus the line inductance tuned by condenser 9. To effectively kill this oscillation circuit the plate III of tube I08 is returned to the side 3 of the line through relay coil H3 and R. F. choke I01. To prevent chattering the armature of the step coll I I8 is shaded by coil I I 5 which may take the form of a single turn of uninsulated copper wire wound around a part of the magnetic coil, so as to allow operation on alternating current.

Each time the step coll III is energized by the dialed signal pulses the step relay arm I28 is advanced one step and switch H1 is momentarily closed. This energizes the anti-return coil II8 which operates a quick acting slow releasing mechanism to prevent the step switch from returnin to its home position as long as switch H1 is momentarily closed and opened in fairly rapid succession. The arm I29 of the step switch is advanced to the desired position and the push button controlled radio starts to tune. While the motor is performing a tuning operation, switch I30 is closed thereby maintaining coil II8 energized which as stated prevents the step switch from returning. As switch H1 is closed only when the step coil of the relay is energized, the return mechanism will be operated when switch I30 is released as soon as the automatic tuning mechanism of the radio has finished its function. The volume control may be accomplished by dialing one pulse to increase volume and two pulses to decrease volume. Switch I is closed only during the tuning operation of the motor and not closed during the volume control operation since at reduced voltage the motor armature is not displaced. Hence, it is necessary to make the last pulse dialed for a volume control operation (which is the first and only pulse in volume reduction), a sustained pulse, that is, sustained until the desired change in volume has been accomplished. As soon as this pulse ceases, switch H4 opens, the step switch stepping coil H6 is deenergized, switch H1 opens and the anti-return coil H8 is deenergized allowing the step switch arm I29 to snap back to its home position I20. This eliminates the necessity for blank positions on the step switch. The turning on and off of the radio would first b completed simply by dialing the desired number to place the step switch arm I29 on the contact I21 or I28. No blank positions are necessary to operate the return mechanism as the switch I I4 opens when the signal pulses cease after con tact is made with I21 or I28, and the step switch thereupon returns to its home position.

The volume control operation may be performed by means of the auxiliary switch 38 shown in Figs. 3a. and 3b. For instance, operation of the switch handle 98 clockwise in either arrangement will be the equivalent of dialing one on the automatic telephone dial mechanism 13 and this will cause the motor 52 (Fig. 4a) to operate the volume control device'so as to increase the volume. This increase in volume continues until the operator releases the switch handle 98 thereby allowing the switch to return to its normal released position. Operating the switch handle in the opposite direction will be the equivalent of dialing two on the telephone dial and will decrease the volume. Here againthe motor continues to operate the volume control device due to the sustained second pulse until the operator releases the switch 98.

, It is, of course, possible to operate the tuning instrumentality of a radio receiver with one electric motor and the volume control device with another electric'motor. Such an arrangement is shown in Fig. 5 of the drawings wherein I39 is the tuning motor and I44 is the volume control motor. Both motors are of the reversible type but only the tuning motor need have a displaceable armature or a relay connected in series or in parallel with the motor, to operate switch I30. In the arrangement shown in Fig. 5 use is made of a two elementglow or arc discharge tube I3I in which the breakdown poten- 'tial is such that the peak line voltage is not sufflcient to start the discharge. However, the tube will break down or start when the potential between the two electrodes I32, I33 thereof is slightly in excess of this value. Once the tube is fired it will conduct at a potential considerably below the breakdown potential. The tube I3l is effectively connected acrdss the conductors 3 and 4 which in turn are connected by means of a plug III to the two conductors of a power supply line. In this case the plug I9 need not be a polarized plug. A series resonant circuit including an inductor III and a condenser 9 is connected between the conductors 3 and 4 in a similar manner as the arrangement shown in Fig. 40. One of the elements I32 of the two element discharge tube I3I is connected to a point of the series resonant circuit intermediate the inductor I0 and the condenser 9. The other electrode I33 of the tube is connected to the conductor 3 through stepping coil I34. Stepping coil I34 op crates a switch I35 which acts to connect an anti-return coil I31 which may be an A. C. operated slow release air dash pot type relay across the tube I30.

the conductors 3 and 4. The stepping coil I34 also operates the step coil arm I38. This step coil arm cooperates with the contacts I5I through I59 of the step switch mechanism. Switch I30 cooperates with the motor I39 and provides a shunt circuit across switch I35 for connecting the anti-return coil I31 across the line 3, 4 to provide an anti-return circuit efiective while motor I39 is energized. The on and oil switch 51 for the radio receiver is operated in one direction by the coil 56 and in the other direction by the coil 58. The station setting commutator discs 63 through 65 are of the same construction as those shown in Figs. 2 and 4a and determine the direction and amount of rotation of the tuning motor I39. The home position of the step switch is the contact point I5I which is blank, that is, this contact point is not connected to anything. From the description of the previous figures it is evident that when the step switch arm I38 is positioned on the contact point I52, the motor I44 will be energized through its motor winding I45, secondary winding of power transformer 55 and arm I38. This will operate the motor I44 in one direction. To operate the motor in the other direction the step switch is operated so that arm I38 contacts point I53. This will energize the motor through the coil I43 and reverse its direction of rotation. The motor is coupled in any suitable fashion to the volume control shaft. Hence, the volume control can be operated in either direction.

The operation of the tuning motor I39 is the same as described in connection with Fig. 4a. The same is true of the on and off switch 51.

Where for one reason or another it is desirable to use a three element gas tube, such, for instance, as an RCA OA4G type tube or a WE 313A type tube for controlling the operation of the step switch, an arrangement such as that shown in Fig. 6 may be utilized. In Fig. 6 the polarized plug I9 is used to connect the circuit to a power supply line which, in effect, impresses the power supply line potential between the conductors 3 and 4. The three element gas tube I60 comprises a cold cathode-like element I63, a main anode IGI and starter-anode I62. This tube is known in the art as a cold cathode glow discharge tube and the discharge can be initiated with a very small amount of electrical energy supplied to the starter anode circuit. This feature of the tube makes it practicable to obtain remote control of line operat'ed electrical devices by means of an electrical impulse generated, say at radio frequencies and transmitted over the same power line. Condenser 9 and inductance coil I0 form a tuned circuit which is connected between the conductors 3 and 4 in the same manner as the arrangement shown in some of the other figures of the drawings. A bleeder circuit comprising a resistor I64 is also connected between the conductors 3 and 4 and the starter anode I62 is connected to a slider which operates along the bleeder resistor I64. The cold cathode I63 is connected to a point of the tuned circuit which is common to the condenser 8 and inductor Ill. The anode or plate I6I of the tube I60 is connected to conductor 3 through relay windings HI and I81 in series.

In the arrangement thus far described substantially the full line voltage is applied between the anode IBI and cold cathode I 63 of The starter anode is biased, that is, it is maintained at a potential just below that required for breakdown by means of the connection to the bleeder circuit I. The inductance III and'the condenser 9 constitute a tuned circuit in series with the line. Thus, when a carrier energy having the frequency of the tuned circuit is impressed on the power line a resonant voltage appears across elements 9 and I0. The effect of the voltage across the condenser 9 is to increase the negative potential peaks on the cold cathode I53 and thereby increase the potentials between cold cathode I53 and starter anode I62. These peaks start a discharge between the cold cathode and the starter anode thereby producing ionization which enables the discharge to take place between the cathode and the main anode IGI provided the circuit values are such that sufficient starter anode current flows. After the discharge occurs between the cold cathode and the main anode, current will flow through the relay windings HI and I91. Because of the fact that the power supply line is alternating current, which means that A. C. is supplied to the anode IBI, the tube I99 ceases to discharge at the end of the positive part of the power cycle when the carrier is removed.

It will be noted that most of the voltage on the starter anode required to cause breakdown is supplied by the bleeder circuit I69. As a result, the tuned circuit is required to supply only the difference between breakdown voltage and applied A. C. voltage. In setting up an arrangement like that shown in Fig. 6 precautions should be taken so that at the highest line voltage, the A. C. voltage applied to the starter anode I62 will not be sufficient to cause the tube I60 to break down and so that at the lowest line voltage the carrier voltage will be high enough to make up for the low line voltage. With an RCA OA4-G type tube suitable operation will usually be obtained by supplying an R. F, starter anode voltage having a minimum peaked value of 55 volts.

The relay winding I 61 acts upon a switch I" which in turn when closed connects the stepping coil I13 of a step switch between the conductor 3 and l thereby energizing the stepping coil. The relay winding I1I acts upon the antireturn switch I99 which prevents return of the step switch while dialing a number. This last named relay winding also acts upon a squelch relay switctrflli. The stepping coil I13 acts upon the arm I 15 of the step switch mechanism which operates along the contacts I9I through I99. In the step switch the contact I9I is blank, that is, it is not connected to anything. The contact I92 is connected through the voltage reducing resistor 48 to the motor winding 99 and then through the secondary winding of the power transformer 55, relay winding 292 to arm I15. Contact I93 is connected through the voltage reducing resistor 41, motor winding 59, secondary of power transformer 55, relay winding 292 to the arm I15. The station selector devices 43, 44, 45 and 46 are similar to those heretofore described in connection with some of the other figures in the case, and the contact points I94, I95, J96 and I91 are connected to whichever segments of the station selector devices happen to be in the contacting position. The contact point I99 is connected to a settable device I" which is similar to the station setting commutators with the exception that it is provided with two projections I8I and I82 substantially at right angles to the strip of insulation between the two segments of the commutator. The projections 2,sea,41a

III and I9! act to open the switch I" when in a vertical position for the purpose of turning off the receiver. The motor 52 is a reversible motor of the same type as has heretofore been described. It should be noted that the relay winding 202 acts upon a switch 200 which is connected in series with homing relay winding I16 between switch I69 and switch I95. The relay winding I16 operates the switch "I and is, in efiect, a return mechanism for the station switch. Switches I10 and 203 are connected between ground and the cathode of an intermediate frequency ampllfier'tubeof the receiver if a superheterodyne receiver is used, in order to squelch the radio set while the dialing operation is going on. The relay switch ZIII is normally closed but is operated by the winding 29! to prevent return of the step switch while the tuning operation is going on.

In order to show how the mechanism is associated with a. push button tuning device a common type of push button arrangement of a radio receiver has been shown generally within the dotted rectangle I11. It will be seen that in this case depressing the button marked "off" is the same as moving the step switch arm I15 up to the position I99. Depressing the push button marked Station A" is equivalent to causing the arm I15 to contact contact element I91. The same is true with respect to the three buttons marked "Station 13," Station C" and Station D" of the push button control with respect to contacts I96, I and I94. The push button marked Volume up corresponds to the contact point I93 and the push button marked fvohune down corresponds to the contact point I92. In this way the set may be operated at the receiver by depressing the proper push buttons shown within the rectangle I11 or it may be operated from a remote point by transmitting the proper number of impulses over the power line to operate the step switch mechanism.

While the arrangements heretofore described are particularly adapted for remotely controlling electrical apparatus over a power supply line it ,is, of course, obvious that the controlling frequency may be transmitted over any line and even as radio waves without the use of any artiflcial conductors at all. In the latter case the controlling frequency may be impressed upon the trigger tube as for instance tube I69 of Fig. 6 by intercepting the control energy with an antenna and tuned circuit arrangement tuned to the frequency of the transmitted control energy. The received energy may be amplified if necessary and then impressed upon the tube. This will, of course, have the same action on the tube as though the controlling energy were impressed upon the tube from the power supply line.

A system of this type is shown in Figs. 3c, 3d and 4b.

The arrangement shown in Fig. 4b is essentially the same as that shown in Fig. 4a, with the exception that in Fig. 4b the controlling energy is picked up by the antenna A and impressed between the grid and cathode of the tube I" through the intermediary of tuned circuit I9 and 9', it being noted that the antenna A is coupled to coil III through coil III. The usual connection to ground is provided through a condenser C. It is apparent that the only reason for plugging in plug I9 into the power line in the case of Fig. 4b is to provide power for energizing the circuits. In conjunction with an arrangement such as that shown in Fig. 4!; it is preferable to use a control frequency transmitter which transmits control radio waves from the controlling point to the controlled point. Two such transmitter arrangements are shown in Figs. 3c and 3d Fig. 3c is essentially like the arrangement shown in Fig. 3b except that in Fig. 3c, the control energy is transmitted to the remote point by means of an antenna A which is coupled to the coil 82 of the tank circuit through winding 82'. case the filament of tube 85 is connected to ground through a condenser C. The plug 69 of Fig. 3c is connected to the power supply line for the purpose of energizing the circuits. However, this is not necessary if a battery B is connected between conductors B8 and 99.

Instead of providing a generator of continuous waves a short train of waves may be set up by a make and break circuit such as shown in Fig. 3d. In Fig. 311, Hill is the telephone dial which operates the make and break switch mechanism I02 according to the number of impulses it is desired to transmit. Th telephone dial switch I02 acts as the make and break device which is in series with the battery B and the tuned circuit comprising inductance L and condenser C".

The arrangement shown in Fig. 3d is essentially a spark transmitter except that instead of a con tinuous succession of sparks only one impulse is used for each actuation of the remote equipment. In other words, one impulse is used for each actuation of the step switch mechanism shown in Fig. 417.

It is to be understood that equivalent systems to those described above are contemplated by the present invention and that the invention is to be limited only by the scope of the appended claims.

I claim: I

1. In a radio receiver provided with an electric motor and an energizing circuit therefor for tuning the receiver to any one of a plurality of wave lengths, a step switch mechanism for controlling the operation of said motor, said step switch mechanism including a movable arm and a stepping coil arranged to step the arm from a home position along a series 01' contact points, means responsive to successive control pulses received at the receiver from a remote point for energizing the step coil with each pulse to thereby cause the step switch arm to advance from its home position a number of steps corresponding to the number of said successive pulses, means for returning the arm to its home position, means including a quick-acting slow-release relay operating to prevent the operation of said returning means while control pulses are being received during a control cycle of operation of the mechanism, and means operating as long as the tuning motor is in operation to prevent the operation of the returning means.

2. In a radio receiver provided with an electric motor and an energizing circuit therefor for tuning the receiver to any one of a plurality of wave lengths, a step switch mechanism for controlling the operation of said motor, said step switch mechanism including a movable arm and a stepping coil arranged to step the arm from a home position along a series of contact points, means responsive to successive control pulses received at the receiver from a remote point for energizing the step coil with each pulse to thereby cause the step switch arm to advance from its home position a number of steps corresponding to the number of said successive pulses, means for returning the arm to its hom position, means in- In this cluding a quick-acting slow-release relay electrically connected with said stepping coil operating to prevent the operation 01 said returning means while control pulses are being received during a control cycle of operation 01' the mechanism, and means included in the circuit of the tuning motor preventing the operation of the returning means while the motor is in operation.

3. In a radio receiver provided with an electric motor and an energizing circuit therefor for tuning the receiver to any one of a plurality of wave lengths, a step switch mechanismfor controlling the operation of said motor, said step switch mechanism including a movabl arm and a step ping coil arranged to step the armature from a home position along a series of contact points, means responsive to successive control pulses received at the receiver from a remote point for energizing the step coil with each received pulse to thereby cause the step switch arm to be advanced from its home position a number of steps corresponding to the number of pulses received, means for returning the arm to its home position, a quick-acting slow-release relay electrically connected with the stepping coil and arranged so as to disable the returning means during the time that successive pulses constituting a cycle of operation of the mechanism are being received, means included in the circuit of the tuning motor preventing the operation of the returning means while the motor is in operation, and further means included in the motor energizing circuit operating to prevent energization of the motor during the time that the arm is returning to its home position.

4. In a remote control system of the type wherein controlling signal currents are transmitted from a remote point to a controlled point, a motor to be controlled and a circuit therefor, a power supply line, a step switch device, said motor circuit including a plurality of selectively operable means adapted to be selected in accordance with the operation of said step switch device for determining the extent of operation of the motor,

a stepping coil mechanism energized by said controlling signal currents, said step switch device being adapted to be advanced step by step by the stepping coil mechanism from a starting position to any one of a plurality of positions and thereby select one of said selectively operable means, means cooperating with the step switch device for applying a force thereto which tends to return the switch mechanism to its starting position, a locking device for preventing the operation of said last named means, a return relay operatively connected to the locking device, an anti-return coil for said step switch device acting upon excitation thereof simultaneously with the energization of the stepping coil mechanism to render said return relay inoperative whereby the locking device prevents operation of the switch return means, means including a pair of switches in series for connecting the return relay across said power supply line, one of said switches being open when the step switch device is in its home position and closed when the step switch device is in any of its other positions, the other of said series switches being normally closed, means included in said motor circuit for opening said last named series switch only while the motor circuit is energized, and means acting upon excitation of the return relay for disabling the motor circuit during the time that the return relay is energized.

5. In a remote control system of the type wherein controlling pulses of signal currents are transmitted from a remote point to a controlled point, a motor the rotation of which is to be controlled in accordance with the number of pulses transmitted, a motor circuit including a plurality of selectively operable means each acting upon selective operation thereof to effect the rotation of the motor to respectively different positions, a power supply line, a step switch device having a plurality of contact positions corresponding to said plurality of selectively operable means, each thereof being connected with its corresponding one of said operable means, a stepping coil mechanism for said step switch energized by said controlling signal currents arranged to advance the step switch step by step from a starting position to any one of said plurality of contact positions to thereby select one of the selectively operable means, means acting upon the step switch device for applying a force thereto which tendsto return the switch mechanism to its starting position, locking means normally positioned to prevent the operation of said last named means, a return coil operatively connected to the locking device acting after completion of a selecting operation by said step switch to unlock the step switch locking means to permit operation of the switch return means and means included in the motor circuit operative only while the motor is in operation for rendering said return coil ineffective to unlock the locking means whereby the step switch device is locked into the selected position during the operation of the motor.

6. The combination with a radio receiver provided with an operable volume control device an delectric driving means for operating the volume control device, of a step switch mechanism connected with said electric driving means for selectively controlling the operation thereof, operation of said step switch mechanism to a predetermined one of its positions acting to operate the volume control device substantially continuously and relatively slowly toward one extreme control position thereof and. in another predetermined position to operate the volume control device in the same manner but toward the other extreme control position thereof, means for selectively generating and transmitting pulses of controlling signal currents, the number of pulses transmitted during any one cycle of operation of said last named means being determined by the number of steps it is desired to advance the step switch mechanism from its home position, means including a quick acting slow release relay device for returning the step switch to its home position after a time interval which is appreciably longer than the time interval between successive pulses of a train of control pulses during any cycle of operation whereby said step switch assumes its home position after the last pulse of a cycle of operation, and operable means for extending the time of transmission of the last impulse of the cycle of operation to thereby maintain the step switch in the desired position a length of time determined by the degree of volume change desired.

7. The combination with a radio receiver provided with an operable volume control device and electric driving means therefor, of a step switch mechanism connected with said electric drivin means for selectively controlling the operation thereof, operation of said step switch mechanism to a predetermined one of its positions acting to operate the volume control device substantially continuously toward one extreme control position thereof and in another predetermined position to operate the volume control device in the same manner but toward the other extreme control position thereof, means for generating pulses of controlling signal currents including a keying device having a lever arranged so that movement thereof from its normal released position to one extreme position transmits a predetermined number of impulses of oscillations, the last pulse transmitted extending over a period of time determined by the length of time the lever is held in the extreme position, the number of pulses transmitted during any one cycle of operation of said keying means being determined by the number of steps it is desired to advance the step switch mechanism from its home position, means including a quick acting slow release relay device for returning the step switch to its home position after a time interval which is appreciably longer than the time interval between successive pulses of a train of control pulses during any cycle of operation whereby the step switch resumes its home position after the last pulse of a. cycle of operation, said extended pulse acting to maintain the step switch in the desired position a length of time determined by the degree of volume change required.

8. In combination with a radio receiver having a tuning shaft and a volume varying means, a motor coupled to said tuning shaft, a plurality of energizing circuits for said motor, a plurality of control circuits for said volume varying means, a controller in each energizing circuit to de-energize said motor in response to movement of said shaft to predetermined positions, a stepby-step switch having a neutral position and a plurality of successive circuit closing positions, means responsive to a plurality of successive im pulses to move said switch from neutral position to certain successive positions in which it closes successive control circuits and to other successive positions in which it closes successive energizing circuits, reset means adapted upon actuation to move said switch to neutral position, circuit means including a normally-closed switch for actuating the reset means, a relay actuated simultaneously with the impulse responsive means adapted to effect the quick opening of the normally-closed switch to thereby disable the reset means during reception of impulses and to effect a slow return of said switch after the reception of impulses and means responsive to the energizetion of said motor to control the effectiveness of said relay, whereby a reset operation is prevented until said motor has been de-energized.

FRANCIS H. SHEPARD, JR. 

